Magnetic Properties of Mn_3−xNi_xB₄ and Mn_3−xCo_xB₄

Abstract

Thermomagnetic properties of Mn_3−xMe_xB₄ (Me=Ni or Co; 0.36≥x>0) were investigated in the temperature range from −196°C to 300°C. The antiferromagnetic characteristics of these compounds are almost similar to those of the parent compound Mn₃B₄ at high temperatures, and a monotonic decrease of the Néel point is observed depending on the amount of Ni or Co present. With decreasing temperature, however, the susceptibility undergoes a transition to ferromagnetic state, and exchange inversions are observed at temperatures between −140°C and −10°C depending on the value of x in the formula. Magnetizations of these compounds are unsaturable even under the field of 18,000 Oe and are as large as 30∼40 e.m.u./g. From the results of the present experiment, the spin assignment in Mn₃B₄ is discussed again. It is concluded that manganese atoms on 4(g) exclusively can contribute to the magnetism.